Apparatus for the preparation of ice cream, milkshakes, sorbets, frozen desserts, and the like, in each case from a pumpable starting mixture

ABSTRACT

An apparatus for the preparation of ice cream, milkshakes, sorbets, frozen desserts and the like, in each case from a pumpable starting mixture, comprises a storage container (1) for the starting mixture and a cooling or freezing cylinder (2) arranged below said container with which it communicates via a supply conduit (25), in which cylinder (2) a stirring and scraping mechanism (9) is arranged, the supply conduit (25) opening into an inlet chamber (7) located at one end of the cylinder (2), a discharge valve (19) being provided at the other end of the cylinder (2), only the cylinder (2) being provided with a heating (6) for pasteurizing the starting mixture, a thermostat (53) being provided to limit the wall temperature of the cylinder (2), and devices being provided for transporting the starting mixture from the inlet chamber (7) to the discharge valve (19). To obtain a bacteriologically safe pasteurization product on the one hand and to eliminate any alterations to the flavor on the other hand, a closable connecting conduit (22), which opens out of the end region (21) of the cylinder (2) adjacent the discharge valve (19), is provided between the storage container (1) and the cylinder (2). A freezing device (62) connected with the cooling aggregate (58) of the apparatus is arranged on the connecting conduit (22) to block it.

The invention relates to an apparatus according to the preamble of claim1.

In an apparatus of the generic type known from German published patentapplication 35 44 802 (corresponding to U.S. Pat. No. 4,680,944) aconnecting conduit is provided between the storage container and the endregion of the cooling or freezing cylinder adjacent the discharge valve,a valve being arranged in the connecting conduit to close off theconnecting conduit. It is thus achieved that the ice cream mix can bepumped through the cooling or freezing cylinder, from there to thestorage container, and back to the cylinder during pasteurization oralso during normal storing operation, when the ice cream mix is kept ata storing temperature slightly above the freezing point. Thus asatisfactory result is achieved from a bacteriological standpoint withcomparatively simple means, while, on the other hand, changes in flavorof the ice cream mix are avoided during pasteurization, since acirculation of the total contents of the cooling and freezing cylinderand of the storage container is made possible during pasteurization. Thevalve to be installed in the connecting conduit is however veryexpensive and some remaining bacteriological contamination cannot bedefinitely precluded.

It is accordingly the object of the invention to further develop theapparatus of the generic type such that a bacteriologically safesolution to close off the connecting conduit is created by simple means.

This object is attained in accordance with the invention by the featuresin the characterizing part of claim 1. The nub of the invention residesin that during normal operation, while servings of ice cream are drawnoff, i.e. while the connecting conduit must be closed, the ice cream mixcontained in the latter is frozen. A possibility of closing is thuscreated with the specific means of the apparatus, namely the coolingaggregate anyway available. If the plug of ice cream mix in theconnecting conduit is to be melted, then the supply of coolant to thefreezing device is switched off.

Further features, advantages and details of the invention will becomeapparent from the sub-claims and the ensuing description of exemplaryembodiments taken in conjunction with the drawing, in which

FIG. 1 is a schematic illustration of an apparatus according to theinvention, seen in a vertical longitudinal section;

FIG. 2 is a cross section taken along the line II--II of FIG. 1; and

FIG. 3 is a schematic illustration of a modified embodiment of theapparatus according to the invention, in a vertical longitudinalsection.

As shown in FIGS. 1 and 2, a storage container 1 is disposed above ahorizontal cooling or freezing cylinder 2--in a conventionalfashion--and with it forms a unit. The side walls 3 of the storagecontainer 1 are provided with a cooling tube 4, which extendsapproximately helically about the side walls 3 and is only schematicallyillustrated.

The cylinder 2 is surrounded by a cooling jacket 5 through which acoolant can be pumped. The cooling jacket 5 itself is surrounded in turnby a heating jacket 6. The cooling jacket 5 and heating jacket 6 extendsubstantially over the entire length of the cylinder 2, with theexception of an area located on one end--seen on the left in FIG. 1--inwhich an inlet chamber 7 of the cylinder 2 is located.

The cylinder 2 is coaxially penetrated by a shaft 8 of a stirring andscraping mechanism 9, which shaft 8 is rotatably supported in end walls10, 11 of the cylinder 2 and extends out of one end--on the left inFIG. 1. The stirring and scraping mechanism 9 is driven on this end byan electric motor 12.

A disk 13 is attached to the shaft 8, leaving only a very narrow gap 14with respect to the wall of the cylinder 2. This disk 13 divides theinlet chamber 7 from the actual cooling and/or freezing chamber 15 inthe cylinder 2, this chamber 15 being surrounded by the cooling jacket 5and heating jacket 6. A helical stirring element 16 is secured on theshaft 8 in the chamber 15. Also attached to the shaft 8 are two scraperblades 17 contacting the inner wall of the cylinder 2, whichcontinuously scrape the ice cream mix from the inner wall of thecylinder 2. Contiguous with the helical stirrer 16, a close-pitch worm18 is also attached to the shaft 8, its worm pitch being such as toexert a certain backpressure effect with respect to the helical stirrer16. A discharge valve 19 is attached in front of the end wall 11opposite the motor 12. In the disk 13 acting as a partition, there maybe a through opening 20 connecting the inlet chamber 7 with the chamber15.

The cooling and/or freezing chamber 15 communicates with the storagecontainer 1 in the end region 21 adjacent to the discharge valve 19 orto the associated end wall 11 via a connecting conduit 22.

The storage container 3, which is closable by means of a cap 24,communicates with the inlet chamber 7 of the cylinder 2 via a supplyconduit 25, which is preceded by a pump 27 disposed in the storagecontainer 1 on its bottom 26. This pump 27 is driven by an electricmotor 28. The pump 27 may be a gear pump. It is preceded, in thevicinity of the supply conduit 25, by a check valve 29, which prevents areturn flow of liquid from the cylinder 2, or its inlet chamber 7, tothe storage container 1.

The pump 27 is also provided with an overpressure valve 30, which opensif the counterpressure coming from the inlet chamber 7 exceeds apredetermined value. In that case, the liquid to be pumped into theinlet chamber 7 from the storage container 1 is returned to the storagecontainer 1 by a short circuit. It is conventional in the trade to equippumps in this way.

The pump 27 has an intake fitting 31, the open end of which is in thevicinity of the bottom 26 of the storage container 1, so that there areno idle spaces in the storage container 1.

A stirrer 33 driven by an electric motor 32 is disposed on the bottom 26of the storage container 1, continuously recirculating the liquidlocated in the storage container 1.

Air is introduced into the upper portion of the inlet chamber 7 via anair line 34. To prevent liquid and/or air from returning to the air line34 from the inlet chamber 7, the air line is provided with a check valve35, which may be embodied by what is known as a lip valve, for example.Compressed air is supplied to the air line 34 by a compressor 37 drivenby an electric motor 36, the compressor 37 being preceded by an airfilter 38. A compressed air dehumidifier 39 follows the compressor.

A compressed air storage container 40 is also provided in the air line34, and a check valve 41 is disposed between this container 40 and thecompressor 37. Between the compressor 37 and the check valve 41, anoutlet throttle valve 42 is also provided, through which some compressedair flows out continuously. Because of the check valve 41, however, nocompressed air can flow out of the compressed air storage container 40back to the throttle valve 42. A pressure monitor 43 is also disposed inthe air line 34 between the compressor 37 and the check valve 41, and itswitches the compressor 37 on whenever the pressure in the air line 34between the compressor 37 and the check valve 41 falls below a certainminimum. This minimum pressure may be on the order of 1.7 bar, forexample. The compressor switches back off again whenever the pressureexceeds a predeterminable maximum pressure, such as 2.0 bar. The airpressure can be monitored visually by means of a manometer 44. The checkvalve 41 is also preceded by a sterile compressed air filter 45. Apressure limiting valve 46 is disposed on the compressed air storagecontainer 40.

A throttle valve 47 and a magnetic valve 48 are disposed in the air line34 between the compressed air storage container 40 and the check valve35. A pressure monitor 49 is also provided between the magnetic valve 48and the check valve 35.

A cooling aggregate 58 in conventional manner consisting of a compressor56 and a liquefier 57 is provided to generate the necessary lowtemperatures. A line 59 leads from the outlet of the liquefier to thecooling jacket 5 of the cylinder 2 in the vicinity of its dischargevalve 19. An expansion valve 60 is provided in the line 59 to expand thecoolant liquefied in the liquefier 57. A suction line 61 leads back tothe inlet of the compressor 56 from the other end of the cooling jacket5.

A freezing device 62 is arranged to surround the connecting conduit 22.This device consists of a tube 63, which helically surrounds theconnecting conduit 22, and which is connected via a line 59a behind theexpansion valve to the line 59 on the one hand and via a suction line61a to the suction line 61 on the other hand. The tube 63 or thefreezing device 62, respectively, is thus connected parallel to thecooling jacket 5 in the cooling circuit of the cooling aggregate 58. Amagnetic valve 64 is located in the line 59a assuring that the supply ofcoolant to the freezing device 62 can be switched off even when coolantis supplied to the cooling jacket 5. The freezing device 62 is made suchthat upon actuation by a coolant the contents of the connecting conduit22 are frozen.

The exemplary embodiment described above functions as follows:

The storage container is assumed to contain a so-called ice cream mix50, that is, a liquid starting mixture for making ice cream, and thatice cream is prepared from this mixture in the cylinder 2, while air issimultaneously incorporated into it.

The ice cream mix 50 is pumped into the inlet chamber 7 of the cylinder2 by means of the pump 27, in accordance with the pressure prevailing inthe cylinder. Except for the starting up phase, when it is not constant,the pressure in the cylinder 2 varies only when servings of ice creamare drawn off by means of the discharge valve 19, and so the pump 27 isalways switched on during or after the drawing of a serving of icecream.

The air needed for aerating the ice cream is supplied via the air line34. The quantity of air to be supplied per unit of time through the airline 34 is set a the throttle valve 47. Typically this may be done suchthat air is forced into the inlet chamber at a rate between 0.8 and 2.7liters per minute. Since the output of the pump 27 per unit of time isconstant and amounts for example to 2.5 liters per minute, thevolumetric ratio of ice cream mix to air that is supplied per minute canbe kept very accurately at a predetermined value.

If the pressure in the cylinder 2 drops because a serving of ice creamhas been withdrawn, then the pressure in the line 34 between the checkvalve 35 and the magnetic valve 48 also drops, and so the pressuremonitor registers this pressure drop. If the pressure drops below apredetermined value, for instance 1.2 bar, then a signal is sent via acontrol line 51 for opening the magnetic valve 48, and a signal is sentfor switching on the motor 28 and the pump 27 via a control line 52. Airand ice cream mix are then pumped into the inlet chamber 7 of thecylinder 2 at a predetermined quantity ratio. Once the pressure in thecylinder 2 has again attained a predetermined maximum value, forinstance 1.5 bar, then by way of appropriate signals from the pressuremonitor 49 the magnetic valve 48 is closed and the motor 28 of the pump27 is switched off. This process is repeated continuously, wheneverservings of ice cream are drawn off at the discharge valve 19.

The storage container 1 is unpressurized; the ice cream mix stored in itis kept chilled at a storage temperature of approximately 2° C. and isperiodically recirculated by the stirrer 33, to assure a uniformtemperature within the ice cream mix.

Throughout this process the cooling jacket 5, on the one hand, and thefreezing device 62, on the other hand, are supplied with coolant fromthe cooling aggregate 58, i.e. the magnetic valve 64 is open. The icecream mix contained in the connecting conduit 22 is frozen, so thatthere is no connection between the cooling and/or freezing chamber 15and the storage container 1 in this area.

As will be understood from the foregoing, the cylinder 2 is alwaysfilled with ice cream mix or with prepared ice cream, regardless ofwhether only a little ice cream mix 50, or a large amount, is present inthe storage container 1. Whenever the ice cream mix 50 still containedin the storage container 1 and the prepared ice cream in the cylinder 2are to be pasteurized--typically after the close of business for theday--the supply of compressed air is shut off by the general closure ofthe magnetic valve 48. At the same time, the stirring and scrapingmechanism 9 and the pump 27 are put into operation. The cooling processvia the cooling tube 4 and the cooling jacket 5 and the freezing device62 is also switched off, and the heating by the heating jacket 6 isswitched on. Due to the heat transfer the ice stored in the cylinder 2is melted and the ice cream mix 50 is further heated. The heat alsoflows into the connecting conduit 22 tightly connected with the cylinder2 and melts off the ice cream mix frozen onto its inner wall. As aresult of the pressure acting upon the melted-off ice cream plug in theconnecting conduit 22 from the chamber 15, this melted-off plug ispressed into the storage container 1. During the pasteurizaton process,the heating jacket 6 is regulated via thermostat 53 that measures thetemperature of the inner wall of the cylinder 2. The ice cream mix ismoved toward the discharge valve by the helical stirrer 16 and fromthere is pumped back into the storage container 1 through the openedconnecting conduit 22 by means of the worm 18, which during operation isused to force the servings of ice cream out through the discharge valve19. From the storage container, the ice cream mix is pumped back intothe inlet chamber 7 by means of the pump 27. Thus a continuouscirculation of the ice cream mix between the storage container 1 andcylinder 2 is attained, and all the regions of the wall of the cylinder2 are scraped. Since the ice cream mix becomes highly turbulent in thecylinder because of the stirring and scraping mechanism 9 and inparticular the scraper blades 17, there is good heat transmission to theice cream mix from the surface of the cylinder 2 that is heated by theheating jacket 6. When the ice cream mix is to be heated toapproximately 72° C. for pasteurization, it is accordingly sufficientfor the temperature of the inner wall of the cylinder 2 to be kept at atemperature of from 75° to 80° C. by means of the thermostat 53. Thisassures that the ice cream mix will not burn onto the inner wall of thecylinder 2 and take on a caramel-like flavor. As soon as all the icecream mix 50 has attained the temperature of pasteurization, which isdetected via a thermostat 54 housed in the storage container 1, theheating jacket 6 is switched off; this may be done in a delayedmanner--under the control of a clock, not shown--to assure effectivegermicidal action in the ice cream mix 50.

The refrigeration system, not shown in the drawing, is then switched onagain, and the ice cream mix 50 is chilled to the storage temperature of2° C., via the cooling tube 4 and the cooling jacket 5. The attainmentof this storage temperature is monitored via a thermostat 55 housed inthe storage container 1. While the ice cream mix 50 is chilled to thestorage temperature and during storing, the magnetic valve 64 is closed,so that no coolant is admitted to the freezing device. While the totalice cream mix is chilled after pasteurization and during normal storingoperation, the connecting conduit 22 is not closed by an ice cream plug.Only when the normal discharge operation is switched on, the magneticvalve 64 is opened with the consequence that the connecting conduit 22is closed by an ice cream plug.

For pasteurization, it is possible to double the speed of the pump 27,in order to increase the recirculation of the mixture. The quantityrecirculated per unit of time between the cylinder 2 and storagecontainer 1 is determined solely by the capacity of the pump 27.

In the embodiment of FIG. 3, elements identical to those in theembodiment of FIGS. 1 and 2 are identified by the same referencenumerals. Elements that in principle are functionally the same but thatdiffer structurally are identified by the same reference numerals,provided with a prime. Description of such elements in detail once againshould therefore be unnecessary.

The apparatus of FIG. 3 has a pressure-tight storage container 1',closed off by a cap 24' that closed in a pressure-tight, air-tightmanner.

A roller-like stirrer 33' that is drivable by an electric motor 32' isdisposed in the storage container 1'.

A supply conduit 25' discharges from the storage container 1' into theinlet chamber 7 of the cylinder 2 and is embodied by a pipe bend ofrelatively large cross section, which discharges into the inlet chamberapproximately at the level of the shaft 8 of the stirring and scrapingmechanism 9. Through this supply conduit 25', compressed air deliveredvia the air line 34 can rise in the storage container 1' as well, whichis why the storage container must be embodied such that it is air-thightand pressure-tight. The supply of compressed air may be effected in theconventional manner, for instance as shown and described in Germanpatent 12 77 877 (corresponding to U.S. Pat. No. 3,402,567); this is notcritical in the present context.

The recirculation of the ice cream mixture during pasteurization iseffected solely by means of the stirring and scraping mechanism 9,including the worm 18.

For pasteurization, the magnetic valve 64 is closed so that no coolantis admitted to the freezing device 62. The recirculation of the icecream mix can take place in the claimed manner. The return flow takesplace freely through the supply conduit 25'. The temperature control andthe termination of the pasteurization process are effected as in theforegoing embodiment.

FIG. 3 also shows the connection of the cooling tube 4 on the storagecontainer 1' to the cooling aggregate 58. The corresponding connectioncan be identical in the embodiment according to FIGS. 1 and 2. It is notshown there only for reasons of space. Another line 59b branches fromthe line 59 to supply the individual cooling devices with coolantliquefied in the liquefier 57 and leads to the cooling tube 4 of thestorage container 1'. A suction line 61b leads from this cooling tube 4back to the suction line 61. In order to assure the possibility ofindividually actuating the cooling of the storage container 1', amagnetic valve 66 is arranged in the line 59b behind its branching 65from the line 59 and serves to close off the supply of liquefied coolantto the line 59b. An individual expansion valve 67 for the cooling of thestorage container 1' is still provided behind the magnetic valve 66.Behind the branching 65 and ahead of the expansion valve 60 stillanother magnetic valve 68 is provided in the line 59, by means of whichalso the supply of coolant to the cooling jacket 5 and to the freezingdevice 62 can be blocked.

Instead of ice cream mix, other starting mixtures can also be used, forinstance for milkshakes, sorbets or frozen desserts, as long as thesestarting mixtures are capable of being pumped, or in other words are inliquid form.

I claim:
 1. An apparatus for the preparation of ice cream, milkshakes,sorbets, frozen desserts, and the like, each from a pumpable startingmixture, comprisinga storage container (1, 1') for the starting mixture;a cooling or freezing cylinder (2) with a first end portion and a secondend portion, an inlet chamber (7) being formed at the first end portionin the cylinder (2), and a discharge valve (19) being provided at thesecond end portion; a supply conduit (25, 25'), which connects thestorage container (1, 1') with the inlet chamber (7); a connectingconduit (22), which connects the second end portion of the cylinder (2)with the storage container (1, 1'); a rotatably drivable stirring andscraping mechanism (9) arranged in the cylinder (2); a cooling jacket(5) surrounding the cylinder (2); a cooling aggregate (58), which isconnected with the cooling jacket (5) via coolant lines (59, 61) for thecooling of the cylinder (2) during the preparation and storage of icecream, milkshakes, sorbets, frozen desserts and the like in the cylinder(2); a heater (6) for the pasteurizing of the starting mixture, whichsurrounds only the cylinder (2); a thermostat (53) controlling theheater (6) for limiting the wall temperature of the cylinder (2) duringthe pasteurizing of the starting mixture; transportation means fortransporting the starting mixture from the inlet chamber (7) to thedischarge valve (19); a pump (27) for transporting the starting mixturefrom the storage container (1, 1') into the inlet chamber (7) and fromthe second end portion--at least during the pasteurizingprocess--through the connecting conduit (22) back into the storagecontainer (1, 1'); wherein the connecting conduit (22) is provided witha freezing device (62), which surrounds it and is fixedly mounted to it,and which is connected with the cooling aggregate (58) via coolant lines(59, 59a, 61, 61a), and wherein, in at least one coolant line (59a), avalve (64) is provided for interrupting any cooling of the freezingdevice during the pasteurizing of the starting mixture.